1. Field of the Invention
This invention relates to a product based on a mixture of alkyl glucosides and aliphatic alcohols which may be used as a foam inhibitor, particularly in the food industry.
Considerable significance is attributed to foam inhibition in the food industry, for example in the production of sugar, in fermentation processes and in the recovery of yeast. By addition of suitable auxiliaries, foaming has to be reduced to a such a level that it does not interfere with the industrial production process.
Certain surface-active substances, for example huminic acids, proteins, protein and starch degradation products, pectins and saponins, such as occur widely in nature, are responsible for the troublesome and, normally, stable foams.
The formation of unwanted foams can be a serious obstacle to production in industrial plants, for example, because the capacity of the plant cannot be utilized or because considerable losses of the starting material used can occur as a result of foaming. Particular difficulties through excessive foaming can occur in a sugar factory in the clarifiers and also in the carbonizing tanks and evaporators.
The auxiliaries used for foam regulation have to be substantially removed during the working up of the end product, for example during the refining of sugar, so that they do not burden the end product. In addition, all the auxiliaries used in the production of foods have to be odorless and free from any taste and, of course, physiologically safe.
In addition, foam inhibitors which enter wastewater after use have to be completely biodegradable.
For economic reasons and to keep the quantities of additives in foods as small as possible, foam inhibitors of particularly high performance are required. High-performance foam inhibitors are distinguished by the fact that they develop their effect without any delay, i.e. spontaneously, achieve a high degree of defoaming and remain effective.
2. Discussion of Related Art
Foam inhibitors which have been proposed for use in the food industry include inter alia fatty acid monoglycerides, fatty acid polyglycol esters, polyalkylene glycols, alkylene oxide adducts with alkyl phosphoric acids, branched fatty alcohol alkoxylates and oligosaccharide alkoxylates and also natural fats and oils. Although rapidly and completely biodegradable, these foam inhibitors are not sufficiently spontaneous in their foam-inhibiting effect and do not remain effective for sufficiently long periods.
The problem addressed by the present invention was to provide foam inhibitors for the production and processing of foods which, even when added in very small quantities, would show excellent spontaneous foam-inhibiting activity and would retain that activity for long periods and, physiologically, would be completely safe. At the same time, they would be completely and rapidly biodegradable without forming metabolites in sewage treatment plants.
It is known that alkyl glucosides are readily degradable and non-toxic. However, it is also known that alkyl glucosides having C.sub.12-1, alkyl chains are powerful foam generators.
Alkyl glucosides are mainly produced by two methods. In the direct synthesis method, glucose is directly reacted with an excess of fatty alcohol in the presence of an acid as catalyst to form the glucoside while, in the transacetalization method using a lower alcohol or glycol as solvent and reactant, a lower alkyl glucoside is initially formed, then reacting with a long carbon chain fatty alcohol in the following step to form the end product.
For example, U.S. Pat. No. 3,547,828 describes the production of a ternary mixture of alkyl oligoglucosides, alkyl monoglucosides and the corresponding free C.sub.11-32 alkanols by the transacetalization process with butanol. To obtain products having reduced viscosities where long-chain alkanols are used, the transacetalization reaction is optionally terminated prematurely so that parts of the butyl glucoside still remain in the reaction mixture. After working up in the usual way, the higher fatty alcohol used in excess is for the most part removed in vacuo, generally to values of less than 2% by weight.
By contrast, European patent application 96 917 describes an improved process for acid-catalyzed direct synthesis with C.sub.8-25 fatty alcohols, in which a monosaccharide, preferably glucose, is added in such a quantity that never more than 10% unreacted monosaccharide is present in the reaction mixture. After working up in the usual way, including removal of the excess fatty alcohol in a thin-layer evaporator, the process gives a product containing 20 to 70% by weight alkyl monoglucoside, less than 10% mono- and polysaccharides, less than 2% by weight free fatty alcohol and, for the rest, alkyl polyglucosides.
It has now been found that certain products containing alkyl glucosides have an interesting foam-inhibiting effect.